1. Field of the Invention
The present invention relates to a system for treating and compressing contaminated gas (water saturated, heavy hydrocarbon natural gas with corrosive impurities etc.) which effectively compresses gas so as to process the contaminated gas into a less polluted, easier to handle and usable gas. Sources of contaminated gas are gas ejected from oilfields etc., off-gas, and vapor-recovery gas etc. discharged from heavy chemical industry facilities.
2. Description of the Related Art
Since natural gas produced along with crude oil from onshore and offshore oil production fields is typically a water saturated, heavy hydrocarbon gas contaminated with corrosive substances such as H.sub.2 S (hydrogen sulfide), a system for performing a designated compression for such gas, in a stage prior to refinement or liquefaction, must change the contaminated gas into a more "user friendly" gas without being affected by the aforementioned water etc., so as to enable an effective compression.
However, historically, no where in the market place was there an offered system for compressing or liquefying gas which enabled effective, easy and low-cost compression and liquefaction, without any adverse effects to the system caused by contaminants, H.sub.2 S, water and the like. For this reason, such contaminated natural gas was turned in the atmosphere at plant flare of a platform.
Obviously, since such burning and releasing impurity rich natural gas into the atmosphere are recognized as factors contributing to environmental pollution, and recently there has been a growing requirement to be able to easily compress or liquefy such natural gas, without suffering any adverse effects from the water and the like, and to make good use of the gas as an energy source, and resources.
For example, an invention disclosed in Japanese Patent Publication No. 5-59378 A is a technique of producing liquefied gas from unprocessed gas effusing from small offshore oil and gas production fields by separating the gas from liquid and solid materials, drying the gas, and cooling to liquefy the gas under pressure.
As for a liquid separating means, a drum liquid separator, as disclosed in published Japanese Unexamined Utility Model Application No. 63-20600, is well known to the public.
In published Japanese Examined Utility Model Application No. 2-45519, a volumetric oil injection type compressor, more specifically an oil injection type screw compressor used at Freon gas plants and COG (coke oven gas) refinement plants, is disclosed.
However, no technique has been disclosed where a compressing system effectively compresses contaminated gas with water, etc., (hereafter referred to as natural gas) such as natural gas, off-gas, and vapor-recovery gas without suffering from any adverse effects of toxic substances, including impurities, in the natural gas.